Geoacoustic Sea Bottom Characterization Using Passive, Cost-Effective Sensors

The Navy can gain a significant operational advantage by knowing the ocean’s seabed properties. It is well known that the seabed type can have an enormous impact on sound propagation and therefore effects detection and classification of underwater targets. Seabed properties often are the unknown wild-card in predicting how ASW and MIW sonar systems will perform. Estimating the seabed properties around the world has proven to be an extremely difficult task with today’s technology. In this proposal, a novel method is presented for passively estimating seabed properties with a cost-effective, autonomous sensor. This new approach can provide a way to vastly increase the coverage of seabed maps at a small fraction of the expense using current technology. Rather than using a sound projector (which typically requires a research or T-AGS ship), we exploit the ambient noise that occurs naturally from wind and breaking waves on the sea-surface. This greatly simplifies the measurements and allows for the development of an autonomous sensor from a buoy or autonomous vehicle (i.e., glider or UUV) for seabed geoacoustic characterization. Although using ambient noise for such an important characterization may seem a bit far-fetched the results are surprisingly good.